1. Field of the Invention
The present invention relates to a curable organopolysiloxane composition and a mother mold for cast molding that is produced by molding and curing the curable organopolysiloxane composition.
2. Description of the Prior Art
Cast molding techniques, in which a urethane resin, epoxy rein, or gypsum or the like is cast and cured within a silicone rubber mother mold to generate a plurality of replicas, are widely known, and replicas formed in this manner from urethane resins and the like are currently used in vehicle components, components for household appliances, and decorative components in construction and the like.
In recent years, considerable emphasis has been placed on the properties these types of cast molded products exhibit when used as components within vehicles or household appliances. As a result, improvements have been introduced, including the use of urethane resins of superior strength, reliability, and texture as the casting resin. However, as a result of introducing such superior casting resins, the mechanical strength of the silicone rubber mother mold used for the cast molding, and the elongation properties required as a rubber elastic body tend to decrease, and the mold release durability also suffers, meaning producing a multitude of replicas with the same shape and quality (for example, surface state) from a single mother mold has become increasingly difficult.
Accordingly, in those cases where a multitude of replicas must be produced, a special curable resin with a low curing shrinkage ratio must first be cast in the silicone resin mother mold, thereby producing an inverse mother mold (master) that corresponds with the shape of the master model, and this inverse mother mold must then be used to prepare a plurality of silicone rubber matrices.
The development of a silicone rubber mother mold with improved mold release durability, which would enable the production of a multitude of replicas from a single mother mold, even if the replicas are produced using casting resins with the types of properties described above, has been keenly sought.
As a result, in order to improve the mold release durability, and particularly the tear strength of the silicone rubber mother mold, methods have been adopted in which reinforced silica fillers that have undergone hydrophobic treatment with a silazane-based compound such as those represented by the formulas (CH3)3SiNHSi(CH3)3, (CH3)3SiNHSi(CH3)2NHSi(CH3)3, or (CF3CH2CH2)(CH3)2SiNH(CF3CH2CH2)(CH3)2; reinforced silica fillers that have undergone hydrophobic treatment with a combination of an aforementioned silazane-based compound and a vinyl group-containing compound, such as those represented by the formulas (CH2═CH)(CH3)2SiNH(CH3)2(CH2═CH), (CH3)3SiNHSi(CH3)(CH2═CH)NHSi(CH3)3, (CH3)3SiNHSi(CH3)(CH2═CH)[OSi(CH3)2]NHSi(CH3)3, or (CH2═CH)Si[NHSi(CH3)3]3; or reinforced silica fillers that have undergone hydrophobic treatment with an aforementioned silazane-based compound followed by a second further treatment with an aforementioned vinyl group-containing compound, are added to, and blended into the raw materials of the organopolysiloxane composition (see patent reference 1).
However, although these methods enable some improvement in the mold release durability, they are still insufficient to generate a silicone rubber mother mold that is capable of producing a multitude of replicas using a casting resin such as a urethane resin or epoxy resin with the type of superior levels of strength, reliability and texture and the like that are considered mainstream nowadays.
Furthermore, the applicants of the present invention have also proposed the use of an organopolysiloxane composition containing a blended alkaline material selected from a group consisting of alkali metal hydroxides, alkali metal oxides, alkali metal alcoholates, and alkali metal siliconates, as a method of improving the mold release durability of a silicone rubber mother mold (see patent reference 1). However, depending on the casting resin used, the silicone rubber mother mold produced from this composition may be prone to decreases in the strength and elongation properties, essential requirements as a rubber, meaning further improvements are still required.
[Patent Reference 1]
U.S. Pat. No. 5,288,795